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Regarding the grading, each Cosmos ADC unit is individually calibrated for the minimal distortions at level -0.5dbfs 1kHz with the typical THD <0.00003% or to say shorter .3-.2PPM. The typical level of 2nd, 3rd, and other harmonics between -135.. -145db for all grades from A to C. Grades are only about the noise, and each unit has a grade mark on the left side of the front panel. In most cases, SNR/Dynamic_Range in the MONO mode is within 127+/-1db(A) it is grade-B Cosmos ADC. Less than 126db(A) means grade-C, from 128db(A) and better grade-A, 129db(A) and better grade-0(very rare grade, and probably redundant, just in case). The MONO mode improves the SNR/DR for 3db, so a grade-A unit typically has SNR 125db(A) in STEREO mode. MONO/STEREO modes are switchable by the UAC2 volume commands, for example, if your Windows volume slider position is less than 50%(0 to 49%) the device works as 2 channel ADC, if more than 50% it is a MONO ADC with summed Left+Right inputs mapped on the Left channel(Right input is always mapped to the Right channel). In the MONO mode, both channels need to be tied together L+ to R+, L- to L-. If you just need low distortion measurements or are fine with doing noise calculations by hand it might be worth waiting for the APU to release. It'll probably be cheaper than the Cosmos ADC.
The third one is a very specialized lens, but gives you results impossible to achieve with the others. The result was so disappointing that I didn't even try to do a loop measurement with the Topping E70 that I bought a month ago.
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On top of that, the addition of +48 V phantom power will make the Cosmos APU, chained with any ADC, in my case it’ll be Cosmos ADC, a top notch combo for any compatible condenser or dynamic microphone out there. Basically, there haven’t been manufactured yet an audio interface having a better performance than the above combo, and I’m referring now strictly to THD+N and dynamics. In terms of gain, the +60 dB pre-amplification will match the max. gain of my Motu M4 and will even outperform Focusrite Clarret’s +57 dB of gain, meaning that Cosmos APU + ADC combo can be successfully used with low-sensitivity mics like AKG D5 and Sure SM7B.
A high level specialist may spend some time building a set of test scripts (that's what Amir did, I think), and then a set of less specialized technicians may run the script for QA 24/7, with 100% reproducibility (within a tolerance), in different facilities accross the world. You are right, my table was not readable (wrong labelling, just modified - indication of switch positions (6.7V |10V) was unnecessary). Hence this description: This is usually done by taking into account the width of the FFT window that is used to compute the levels for each frequency. Customers are to bear the consequences and fees incurred, if the parcel was undelivered due to any of the following situation: But, why does it work this way?? Is it a Topping DAC thing or an REW thing? The levels didn't change.
Almost perfect white noise spectrum, with only a bit of low frequency rise. The chart starts at 2Hz so performance is better than it looks at first glance. With these settings the white noise is -187dBFS at 1kHz. A) We offered our 9038S/D DACs users to control the distortions performance of those DACs with the TWEAK9038 Android app. As you noted, what's happening here is that the graph shows a +60dB gain applied to the noise floor. So if we look at 17kHz and that -89dB noise, it's actually -89-60dB=-149dB. LEDs on the front panel work as a "Signal" indication - green if the STEREO mode and the input > -30dbfs, or blue in the MONO mode. A "Clipping" red-LEDs indicate that the input level reached 0dbfs. i.e. 80s style as I believe ;) E1DA Cosmos ADC is a high-performance Analog-to-Digital Converter that can be used for measurements of ultra-low THD+N signals or calibrating Desktop DAC's for minimum distortions. E1DA has professionally designed the Cosmos ADC with premium ESS Sabre ADC Chip. It can also be used to measure the performance of high-fidelity desktop DAC systems with great precision. High-Performance ADC Chip From Sabre Technologies:-
Given the existing measurements performed already by @Archimago ( http://archimago.blogspot.com/2022/05/early-look-cosmos-apu-high-performance.html) and @WolfX-700 ( https://www-l7audiolab-com.translat...l=auto&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp) it makes no sense for me now to upload my own measurements here, but I got similar figures as they did, so this APU really shines and makes a great addition to anyone needing a cheap device to "upgrade" an existing ADC.I understand that variable and pretty low input impedance is a trade-off and required to reach high performance. Just keep in mind that this a challenge in some (rare) applications. I designed a buffer to deal with this. A symmetrical power supply output for powering such buffers would be nice.
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